i don't know if this counts but i had to take the same car with coworkers every day for six months at a job i worked once. It was really far and took 45-60 minutes to get there. sense it was early in the morning i just slept through most of it.
I don't carpool but I hate riding in cars with people because there's so much pressure to talk. Suggestions: Have the music up a little bit louder than usual so that it's not silent ... also, think beforehand of a few topics to talk about.
I had to carpool with some workers a couple a times for training in another town. It was kind of bad since it was only me and the other person each time. If it was a bigger group it would be much easier to be quiet and just blend in. But yeh, pretty awkward conversation both times. I tried desperately to think of topics. One was pretty conversational on their own, but the other was pretty shy as well so it was like double the awkwardness. I also didn't drive cause I would be nervous anyway and I dunno I would feel kind of like I'm being watched.
But like others have said I would try to come up with topics beforehand so you sort of have a plan to what to talk about.